Hyperglycemia vs. Hypoglycemia: What’s the Difference?

Glucose (sugar) is the body’s main source of energy, which is why it’s important that blood sugar levels remain steady. When levels aren’t steady, hypoglycemia (low blood sugar) or hyperglycemia (high blood sugar) can occur. Both can be dangerous and require treatment. 

Diabetes is the most common cause of both hypoglycemia and hyperglycemia. There are some other causes, but it’s pretty unusual for people who don’t have diabetes to have either one.

Because they are inverse conditions, hypoglycemia and hyperglycemia have different symptoms and treatments. And, with both, the symptoms differ from person to person. Some people may not experience symptoms at all.

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What are hypoglycemia (low blood glucose) and hyperglycemia (high blood glucose)?

Hypoglycemia, or low blood glucose, happens when the amount of sugar in your blood is too low. That’s a glucose level of less than 70 mg/dL on a glucose meter (glucometer), continuous glucose monitor (CGM), or other blood test.

Hyperglycemia, or high blood glucose, happens when the amount of sugar in your blood is too high. For people with diabetes, this is anything above 180 mg/dL. High blood sugar is the main reason for long-term health complications related to diabetes.

The best way to know your blood glucose level is to test regularly with a glucometer, a small handheld device that you can use at home. Better yet, use a CGM, a wearable device that uses a sensor under the skin to measure glucose in the body’s tissues. Both devices will give you results in real time.

Target ranges for blood glucose can be different depending on your age and overall health. But in general, glucose target ranges are as follows:

• Without diabetes: For people who don’t have diabetes, a healthy target range is 70 mg/dL to 140 mg/dL.

• With diabetes: People with diabetes typically have a target range of 80 mg/dL to 180 mg/dL.

Causes of hypoglycemia vs. hyperglycemia

Diabetes is by far the most common cause of hypoglycemia and hyperglycemia. 

Hypoglycemia

Hypoglycemia is most common in people with Type 1 diabetes. But it’s possible for those who have Type 2 diabetes or gestational diabetes to have it, too.

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People with diabetes have to constantly balance medications with food and exercise to keep blood glucose levels within a healthy range. That can be challenging, as every day is different. It’s not surprising that some days glucose levels run too low or too high. 

When you have diabetes, common causes of hypoglycemia include:

• Too much exercise

• Too much of any diabetes medication (insulin, sulfonylureas, glinides)

• Illness

• Skipped meals

It’s uncommon for people who don’t have diabetes to have hypoglycemia. But, in rare cases, it can happen because of certain medications and medical issues, including:

• Excess alcohol consumption

• Prolonged exercise

• Critical illness (sepsis and liver, kidney, or heart failure)

• Malnourishment

• Adrenal insufficiency

• Tumor of the pancreas that produces insulin (insulinoma)

• Nonislet cell tumor (a rare tumor that produces a hormone similar to insulin)

• A complication of gastric bypass surgery

Hyperglycemia

Diabetes is the most common cause of hyperglycemia. In fact, a high blood sugar level is the test that’s used to diagnose diabetes. Diabetes treatment aims to keep glucose levels within a healthy range but, even with a good diabetes treatment plan, they can creep up. 

Common reasons for hyperglycemia in people who have diabetes are:

• Not taking enough diabetes medication 

• Eating more or exercising less than planned

• Equipment issues with an insulin pump (kinked tubing or site, low battery, out of insulin)

• Improperly stored medication (insulin or other medications not kept at a safe temperature)

• An acute illness, like an infection

• Stress

• Hormone imbalances, such as during growth spurts, menstrual cycles, or menopause

• Dehydration

Like with hypoglycemia, it’s unusual for an otherwise healthy person to have hyperglycemia. For people who don’t have diabetes, an underlying medical issue or medication can cause hyperglycemia. Examples of these are: 

• Hospitalization with any severe illness

• Cushing syndrome

• Polycystic ovary syndrome (PCOS)

• Certain medications, such as steroids

Symptoms of hypoglycemia vs. hyperglycemia

Symptoms of hypoglycemia and hyperglycemia range from mild to severe and differ from person to person. It’s important to identify what they feel like for you, so you can spot the warning signs early.

Hypoglycemia

People may notice the following symptoms when their blood glucose level is below 70 mg/dL:

• Sweatiness

• Shaking 

• Dizziness 

• Confusion 

• Fast heartbeat

• Hunger

• Feeling weak or tired

• Feeling nervous or upset

• Headache

In many cases, you’ll notice if your blood sugar is too low. But some people with diabetes experience few or no symptoms with hypoglycemia. This is called hypoglycemia unawareness, and it affects about 40% of people who have diabetes.

Hypoglycemia unawareness is a problem. Symptoms are the body’s way of alerting you to a problem, so that you can fix it. If you don’t know that your blood glucose level is dangerously low, you probably won’t treat it. So it continues to drop, and you can become very confused, drowsy, pass out, or have a seizure.

Hyperglycemia

As with hypoglycemia, symptoms of hyperglycemia range from mild to severe. They are also different for different people. Some people might not have any symptoms at all.

Common symptoms of hyperglycemia are:

• Dry mouth 

• Increased thirst

• Frequent urination 

• Headache

• Blurry vision

• Nausea

• Feeling weak or tired

• Shortness of breath

• Fruity-smelling breath

• Vomiting

• Flu-like symptoms, like feeling achy or unusually warm or cold

Some people are more sensitive to the symptoms of high blood sugar than others. Often, people can tolerate glucose levels that are just slightly out of range. But, as glucose levels get higher, symptoms often become more severe.

How is hypoglycemia vs. hyperglycemia treated?

Treatment for either depends on many factors, including which type of diabetes you have, what your blood glucose level is, and the instructions from your diabetes care team.

Hypoglycemia

You can treat hypoglycemia with fast-acting carbohydrates, using the “15-15 rule”: 

• Ingest 15 g of fast-acting carbohydrates.

• Wait 15 minutes.

• Check your blood glucose level again. If it’s still below 70 mg/dL, repeat the cycle.

If you have diabetes, carry sources of fast-acting carbohydrates with you at all times. Some examples of a 15 g serving are:

• 4 glucose tablets

• 1 tube of glucose gel

• 1/2 cup of fruit juice or regular soda

• 6 large jelly beans

• 1 tbsp of sugar or honey

If your blood glucose is below 55 mg/dl, you may need medical attention. Some people are prescribed glucagon (or similar emergency medication), which can quickly raise blood sugar. If you have this, make sure you and your helpers know where it is and how to use it. Teach others to call 911 if you:

• Don’t respond to fast-acting sugars

• Can’t eat or drink

• Have confusion or trouble talking or walking

• Pass out or have a seizure

Hyperglycemia

If you have hyperglycemia, be sure to follow the instructions your diabetes care team gave you. This might involve exercise or extra insulin, depending on what type of diabetes you have and what medications you’re taking. If your blood glucose is over 240 mg/dL, be sure to check your urine for ketones. When in doubt, call your healthcare team sooner rather than later. This will give you a better chance of preventing your blood glucose from reaching a dangerous level.

Hypoglycemia vs. hyperglycemia: Is one worse than the other?

Both low blood glucose and high blood glucose can lead to life-threatening emergencies. This is why it’s important to recognize the signs early and know the difference. Left untreated, both hyperglycemia and hypoglycemia can worsen and be very dangerous.

Managing diabetes is a balancing act. If you have diabetes, you will most likely have high and low blood glucose levels now and again. (There’s no being perfect when it comes to managing diabetes.) But, if your blood glucose levels are often outside of your target range or you’re noticing lots of ups and downs, it’s a sign you could use some extra help.

Can a person have both hypoglycemia and hyperglycemia?

Yes, a person can have both high blood glucose and low blood glucose, but not at the same time. Blood glucose levels are always changing. Because of this, most people who have diabetes see their levels rise and fall throughout the day. 

Using daily management tools, such as a glucometer or CGM, can help you decrease out-of-range glucose levels. 

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Written by:

Jewels Doskicz, RN, BA

Jewels Doskicz, RN, BA, is an Arizona-based registered nurse with 22 years of hospital-wide clinical nursing experience and 11 years of medical writing and editing experience. She was a former healthcare content creator for a digital health tool at HealthLoop and director of clinical content operations at GetWellNetwork.

Edited by:

Sophie Vergnaud, MD

Sophie Vergnaud, MD, is the Senior Medical Director for GoodRx Health. An experienced and dedicated pulmonologist and hospitalist, she spent a decade practicing and teaching clinical medicine at academic hospitals throughout London before transitioning to a career in health education and health technology.

Reviewed by:

Mandy Armitage, MD

Mandy Armitage, MD, has combined her interests in clinical medicine with her passion for education and content development for many years. She served as medical director for the health technology companies HealthLoop (now Get Well) and Doximity.

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